New ways to trick your tummy to feel full on less

(USA TODAY) -- Researchers are uncovering new ways to trick your tummy so you eat less at meals.

Nutrition scientists at Pennsylvania State University have shown that people who eat a broth-based bowl of vegetable soup; a large, low-calorie, lettuce-based salad; or an apple before a meal consume about 110 to 190 fewer calories at the meal, including the calories in that first course.

They also have shown that people can feel full on fewer calories if fiber-rich vegetables (broccoli, spinach, carrots) and fruits (berries, peaches) are added to standard recipes and menu plans. This means the entrees contain fewer calories per bite, which is called lowering the energy density of the dish.

Now, the researchers have found that people significantly reduce their calorie intake at a meal if both the portion size and calories-per-bite in the entree are reduced by as little as 25%.

People did not rate their feelings of hunger or fullness any differently when the portion size and the calories-per-bite were reduced that much.

"The take-home message is you need to watch what you are eating over the whole meal, especially the entree, because that is where you get most of your calories," says Barbara Rolls, a professor of nutritional sciences and author of The Ultimate Volumetrics Diet with Mindy Hermann. "Putting more vegetables into the entree is a win-win situation, because you are eating more vegetables and you are cutting the energy density, so you end up eating fewer calories overall."

Managing portion size as well is important, says Rachel Williams, a Penn State doctoral student. If you don't serve yourself a large portion, you're going to be less likely to eat as much at the meal, especially if you are serving yourself an entree packed with vegetables, she says.

Although there were no men in the study, the results probably apply to men, too, Rolls says.

In practical terms, this means:

-- Add vegetables such as spinach, zucchini, yellow squash, broccoli, carrots, peppers and onions to lasagna, casseroles, pasta dishes and pizza to lower the calories in each bite.

-- Increase the proportion of vegetables in stir-fry dishes, broth-based soups and stews.

-- Add extra vegetables to sandwiches.

-- Sneak purees and chopped vegetables into tomato-based dishes, where they are hidden by the strong flavor and bold color of the sauce. Cook frozen or fresh white vegetables (such as cauliflower, parsnips, onions), orange vegetables (carrots, pumpkin, winter squash) or green ones (broccoli, spinach), and then puree or chop and add to the sauce.

-- Substitute vegetable or fruit purees for half or even two-thirds of the added fat in quick breads and muffins.